Since SARS-CoV-2 is now endemic in the worldwide human population plus some animal species it's impossible to avoid the spread. We can slow the spread to a limited extent but eventually all of us will be exposed.

Maybe it is - if so, not fighting it consequently in many regions of the world certainly helped with that. But slowing the spread is still of essential importance. We do have vaccinations, which greatly reduce the risk of getting infected and especially the risk of severe consequences. Still, the very vulnerable groups of our society are carrying a considerable risk even when vaccinated. That alone should mandate to keep infection count low. And the more we vaccinate and have other limiting means in place - like wearing masks in indoor public places where it is possible - the lower the infection count is. That directly saves quite a few lives and a lot of health, but most of it, it buys us time.

Yes, probably everyone gets exposed to the virus in the future, but we can decide how quickly. Every month later means we might get vaccines which protect close to perfection, that we find better medication or at least better understand what Covid-19 is all causing and can treat better. Also, with any additional infection the risk of another significant mutation increases. Even with current vaccines, with a high enough vaccination rate any outbreaks should be much smaller and more localized. This does make a difference.

Mandatory xkcd: https://xkcd.com/2448/

Hmm, this is a very serious hypothesis. While not disputing it as a viable hypothesis, do we have good models that support this conclusion? Also, how do these (SEIR?) models distinguish E=100 from E being an aggregate of different variants, delta etc? Finally, what is the relationship between E=100 and R0? I wouldn't expect it to be fixed (model independent) but rather a given model will assert some relationship between E and R0.

Sorry if this is a lot of questions, I do think it's valuable to address this with actual models and supporting data.